Rosie the Scientist
by lizinnia
Summary: This story follows the development of Sherlock, John, and Rosie as a family in a series of short snapshots of their lives, in which Rosie is always doing some sort of experiment.
1. Chapter 1

Sherlock put down his cuppa and raised an eyebrow at his friend who was clearly struggling with his daughter.

"Rosie, why do you keep throwing the rattle if you want it? Just keep the rattle!" exasperated John as he leaned over to pick up the toy and hand it to the crying infant in front of him."

"She's learning, John."

"Doesn't seem like she is. She keeps making the same mistake _over_ and _over_ ," John scoffed.

"She's experimenting, learning, teaching herself. She is discovering gravity, physics. She is uncovering the differences between dropping things and throwing things. How fast does it fall? What sound does it make? She is learning about angles and force and how they affect the trajectory the rattle travels. She is smarter than you give her credit for. She knows that the rattle will fall on the ground and she will be upset, but she also knows that her father will pick it up and give it back to her and she will be able to resume her experiments. The world is still so new to her and she has so much to discover. She's grasping at it and taking it in, slowly uncovering the mysteries it holds," Sherlock mused.

"So basically, she's doing experiments and doesn't care that she's making a mess because she knows I will just clean after her and do whatever she wants anyways?"

"Yes."

"Well that's familiar."

They give each other knowing looks and hold each other gazes for a lingering moment, then they break into giggles.

John missed this. 221B. Sherlock. Smiling and cracking jokes with the taller man. But this was different. The way Sherlock talked about Rosie was… unexpected. Sentimental. At some point they must have stopped laughing because Sherlock was sitting there staring at him openly, quizzically.

"Ahem. Right, well," John began with no follow-through.

He thought Sherlock would be annoyed by having a baby around, but clearly the man cared about her, was fascinated by her, even. John knew he would be a good godfather, in his own way.

Sherlock was simply sitting in his chair tea in one hand and mobile in the other, too distracted to notice John's awkwardness. John sat in his own chair and watched the other man's face as he scrolled through Twitter, scoffing at _idiots'_ comments. He felt a wave of fondness flowing through his chest. Maybe this was it, his opportunity to have The Talk. He needed to get it over with at some point anyways.

Sherlock felt his gaze and looked up.

"You're doing a look," he stated.

"Yes, well I have something I'd like to say," John replied.

"I see."

"It's been… difficult, lately. Being a single dad, working at the clinic, having to get people to watch Rosie all the time, and I was thinking… hoping... that since you seem to think she's so interesting and the two of us are here so often already, you would see your way to… you would allow us to…" John spluttered.

"You want to move back in," Sherlock, deduced. This has different from his usual deductions, however, he usually looks so confident, smug even, but now he looked surprised, anxious, confused.

"Yes," John admitted. "I know it's asking a lot from you, having a baby around all the time. You could always call a sitter or drop her off somewhere else if I'm not home and you don't want to deal with her. We'd have to get this place a bit more baby-proofed and there wouldn't be any more experiments in the house," his eyes jotted downwards at that last comment.

"Actually," John paused. "This is asking way to much from you, you never wanted this," John muttered.

Sherlock just stared at him blinking in shock. After taking a few moments to absorb what John was asking up him, his brain caught up with John's current uncertainty and withdraw.

"No!" Sherlock bellowed. "I mean… no it's fine. It's all fine," he said, softer this time.

"Come home, John. You were never meant to live in the _suburbs_."

John's eyes lit up as he looked at his friend in front of him who was clearly holding back his excitement as could be told by the rapid tapping of his shoe and fingers.

"Yeah, you're right," John smirked. "So I'll call an estate agent and get things sorted as soon as I can- if that works for you."

"Of course, John. You and Rosie are always welcome here," Sherlock beamed.


	2. Chapter 2

It was a long day at the clinic: several patients had the flu, one with whooping cough, one with a middle ear infection, ringworm and a patient with a UTI. He trudged up the stairs to 221B in need of a nice cuppa and instantly began to feel the tension in his body ease away when he heard a familiar, low voice.

He opened the door Sherlock and Rosie in the kitchen in matching lab coats and goggles. Rosie's coat was obviously too big for her even with the sleeves rolled up, and the goggles covered a very large portion of her face. John smiled. On the counter there were multiple experiments lined up, many of which John was familiar with from early primary school. There was a glass of water with a straw in it to teach about the refraction of light, a water bottle with shifting particles in it: the remnants of a model tornado swirling around, a volcano that left quite the mess, and now the two were hovering over petri dishes, Rosie on a stool so she could get a better look. John's heart tugged at the image, his day instantly forgotten.

"Do you see the gelatinous material on the bottom?" Sherlock questioned.

"Jello!" Rosie replied.

"Yes, like Jello, but not for people, for bacteria. It contains soy and casein peptones which provide amino acids and polypeptides. These molecules contain nitrogen and nitrogen is very nutritious for microorganisms. We will use these plates to cultivate bacteria found on surfaces around this flat."

"So it's food for germs?" Rosie asked.

"Yes. Food the for bacteria we are going to collect and watch grow," Sherlock explained.

"Cool! I want bac-ter-um," Rosie enthused.

"Bac-te-ri-a. Now, let's go collect some samples," Sherlock grinned, holding out swabs for him and Rosie.

John closed the door behind him, catching the attention of the two 'scientists'.

"Daddy!" Rosie plopped off her stool and clumsily ran over.

"Hey, Love!" John beamed, arms open to catch the incoming child in an embrace. "I see you're doing some fun experiments with Sherlock, huh?"

"Yea! We made a volcano and a tornado!"

"I see that," John smirked looking at the mess on the counter, eyebrows raised.

"Don't worry, John, everything was completely safe and the mess will be gone soon enough."

"And who's gonna clean it? Me or Mrs. Hudson?" John teased.

"Well that depends on whether or not Mrs. Hudson decided to go on that date with the butcher. After our conversation earlier, I suspect not. She will be disappointed about her lack of plans for the evening and will come up here, see the state of the counters, and start incessantly cleaning everything. Most likely in… 27 minutes," Sherlock speculated.

"Right. Well you two should go back to your bacteria," John released his daughter, gentling pushing her in Sherlock's direction.

"Daddy! Do it with us!"

"Alright, alright" he smiled. "Let's go collect some bacteria."

Rosie smiled and ran back to Sherlock. He handed her a few swabs.

"Now, go to the places where you think there will be the most bacteria. Think of places you touch the most, and rub this swab on the area. Don't forget which swab you used on which surface, and don't use the same swab on more than one. Then we'll see which one grows the most bacteria."

"Come on daddy!" Rosie reached up to grab John's hand and pulled him towards the bathroom.

When the swabs were all collected and the plates prepared, Sherlock stacked them and put them away while John left Rosie in the room upstairs to play with her L.O.L. dolls.

John made them tea, then him and Sherlock sat at their respective spots in the sitting room. John with the paper in hand, Sherlock with his laptop.

"You're great with her, you know," John commented, eyes locked on the paper. "She really likes spending time with you."

"Yes, well she shows great interest in my experiments and The Work. She's a Watson through-and-through."

"Yeah, us Watson's love watching you muck about," John consented. "But really, you mean a lot to her. You're more than just entertainment, Sherlock. You opened your home to her. You care for her. You teach her. Hell, you spend more time her than I do. You watch her when I'm at work and then continue to spend time with her when I get back," John explained.

Sherlock looked up from his laptop to study John's face.

"John, I'm sorry if I've overstepped. I didn't mean to take your place as her father or make her as attached to me as she is to you. I'll stop," Sherlock reassured.

"No, no that's not what I'm saying at all, Sherlock. I'm glad you spend a lot of time with her. She needs someone to be consistent in her life," he sighed. "Maybe I should stop working at the clinic, spend more time here with you two."

"Yes, I think that would be a good idea," Sherlock agreed. "We can take more high-profile cases. I'm sure Mycroft has a lot of uses for us. Could pay well."

"Okay, we can take more of those cases, but maybe not Mycroft ," John cringed.

"Yeah, you're right. I can't believe I suggested that , " Sherlock chuckled.

"You must really want me back around," John laughed.

Sherlock stiffened. The air filled with tension.

"You know, you were right," John stated.

"Hmmm, yes. About what?"

"You are like Rosie's father. Maybe even more so than me."

"John, like I said I can-"

"No. No it's not that. It's just it seems wrong that she doesn't have any real label for you."

"I'm her godfather."

"Yes, but she doesn't have anything to call you besides 'Sher'. It seems wrong that twenty years from now when she's an adult who has known you her entire life and was raised by you, she'll just be calling you Sherlock."

"You mean…"

"Yes."

"You're implying that…"

"Yes."

"You're going to stay?"

"What? What are you talking about?"

"You said I'm going to raise her. That I'll spend the next 20 years with her."

"Yeah. Christ, Sherlock, I'm sorry that's a huge assumption to make, isn't it. We don't have to stay here, we can move out or even just spend more time in 221C instead of being here all time time."

"No, John. No."

John looked at the taller man's eyes and swore he saw a red ring beginning to form and...tears hiding towards the back of his eyes.

"What about when you have a new girlfriend and get married again? I'm assuming the woman wouldn't want to stay here with me. She'd probably be made uncomfortable by me being such an influence on her step-daughter. Your girlfriends dislike me enough as it is," Sherlock drawled.

"Well that's because you kept deducing them and insulting them and never bothered to learn their names," John laughed.

Sherlock's expression did not match John's jovial tone.

"Look, Sherlock. This is it. For me. I don't want to start dating again. I'm staying here."

Sherlock's eyes snapped up.

"Oh."

He was confused at first, then relaxed as reality sunk in. He suppressed a large grin from planting itself on his face.

"Okay," Sherlock nodded.

"Okay. Glad we got that straightened out. Now back to what I was trying to say. You're like a father to her. It doesn't make sense for her to just call you 'Sherlock'"

"What else would she call me? That is my name, John."

"Dad," John stated simply.

Sherlock's eyes squinted as he looked at John. His foot was tapping and he licked his lips: nervous. His fists were clenched: uncomfortable with the intimacy of this conversation. His face was… open: sincere . Sherlock's face slackens.

"That might get confusing," Sherlock stated, no longer able to suppress the grin spreading across his face.

"Yeah, it might. But it's the only title that fits unless you have something else in mind. She's a smart cookie; she'll be fine."

"She's been calling me Sher for so long how do we get her to just… change that?"

"Why don't you go talk to her" John says, tilting his head towards the stairs.

"Yoohoo! Boys!" A voice called from the door.

John checked his watch.

27 minutes.


	3. Chapter 3

"Daddy! Where's Papa?"

"He's on a case sweetheart. He's gone out to catch criminals so they can't hurt people anymore," John explained.

"But he left forever ago and he promised he would help me with my science fair project. He promised!"

"I know, and I'm sure he will be home soon. He knows how important this is to you, but sometimes things come up. Do you want me to help? I know a thing or two about science myself. I _am_ a doctor."

"I want Papa!" Rosie screamed, on the edge of having a full-blown tantrum.

"Alright, alright," John assured, a tinge of annoyance in his voice. "Papa will be home soon and you two will do the experiment together. I'll shoot him a text okay, telling him to come home as soon as he's free. For now would you like to hang out with me? We can watch Gumball."

Rosie smiled slightly at that but rolled her eyes when her father noticed.

"Okaaaay, but only until Papa comes home."

"Of course," John said, patting the seat on the couch next to him. Rosie sat down, leaning on her dad. As she was getting comfy, John sent Sherlock a text.

 _Where are you? Rosie is waiting for you. Come home._

Two episodes later, Rosie was starting to fall asleep and John was getting restless. It wasn't unusual for Sherlock to stay out late when a case was on; it would be concerning if he didn't, actually. But this felt wrong. Sherlock made a promise, and while lying and being inconsiderate is typical Sherlock behavior, this wasn't the case with Rosie. He always told her the truth and always made sure to follow through on his promises to her, it's part of the reason why they had such a great relationship. John wished he and Sherlock could have that too.

 _It's getting late. Rosie's falling asleep. You might want to catch the guy and hurry on home now._

…

 _Seriously, Sherlock. You're worrying me._

…

 _That's it. I'm calling Mycroft._

…

His threat left without a snarky reply from the detective, John started to really panic. Sherlock was not okay. And John was stuck here. He couldn't leave Rosie, and if he called a babysitter she would surely pick up on what's happening. He decided instead to text Greg.

 _Is Sherlock with you? He was supposed to be home hours ago._

 _ **He was this morning but he said something about a speckled bracelet and dashed off. You know what he's like.**_

 _Yeah. Thanks Greg._

Great. Sherlock ran off by himself again.

 **Do you want me to gather some officers and look for him?**

 _No, it's okay. Ta._

It most certainly was not okay, but John knew someone who was faster.

 _Sherlock's missing. Last seen at a crime scene at the attached location. Said something about a speckled band then ran off._

 _ **Thank you, Dr. Watson. My brother will be returned shortly.**_

John sat up straight in his chair and tapped his foot. Rosie was babbling about some nonsense John couldn't pay attention to, instead just responding with "uh-huh" unenthusiastically.

By the time Rosie fell asleep, John couldn't take it anymore. He got up off the chair and just as he reached over to grab his coat he heard footsteps stumbling up the stairs.

He sighed with relief and hung his coat back up.

Sherlock blundered through the door, limping and grasping the door frame to stabilize himself. His face was bruised and bloodied. There was a cut through his trousers and a large blood stain that was spreading from an open wound.

John froze, feeling every muscle in his body clench. He took in deep breaths, knowing he had to calm down. Their daughter was sleeping just a few feet away, and he certainly didn't want her to see Sherlock like his. He grabbed Sherlock's wrist, giving him his best Captain look, then dragged him to the bathroom.

"What happened?" John gritted through his teeth.

"Someone clearly didn't like that I was investigating them," Sherlock replied.

"Why did you go off on your own? You _know_ alone doesn't 'protect' you. Hmm? You need someone to watch your back. You at the very least need to tell someone where you're going so they can find you if… God! For a genius you can really be so...so…" John sighed and grabbed his medical kit.

"John, I'm… sorry," Sherlock uttered.

"Right. Trousers off," John ordered and Sherlock obliged, flinching as he pulled them down past the wound, then sat on the toilet seat to be examined.

"Rosie was waiting for you, you know," John stated as he poured antiseptic on without warning.

Sherlock hissed at the sting.

"Yes. I know.

"We were worried about you. You didn't answer my texts."

"I couldn't."

"I had to text Mycroft and get him to drag you back here. Wish I could have done it myself but you know, couldn't leave the flat."

"Yes."

Somehow, Sherlock's terse responses made John's temper even worse. The git could have died _again_ and he didn't care. He still didn't care after everything they've been through.

"Christ, Sherlock you have a daughter now!" John yelled. "You have a daughter who loves you and wants, _needs_ you to come home at the end of the day. And I do too. Did you even think about us? Did we pop into your mind once while you ran off on your own and got yourself stabbed? Huh? Don't we mean _anything_ to you?" John seethed.

Sherlock physically recoiled.

"John, you _know_ you do. You know how much I care about the two of you. I made a mistake, John that doesn't mean I… how _dare_ you insinuate I… you know that I-" Sherlock retorted.

John sighed and placed his hand on Sherlock's knee.

"-I know. I know you do," John placated. "I'm just angry, okay? And I have every right to be. You need to take better care of yourself."

"I know."

"Rosie loves you, alright? And me too. We're a family."

"Yes."

"I can't always be there to watch out for you anymore. I know your job is dangerous and that's something we have to just deal with, but you can at least stop going out of your way to get yourself hurt."

"Okay," Sherlock replied with a look on his face like a reprimanded child.

"Alright," John quipped, securing the gauze on Sherlock's leg. "The adhesives should keep your wound closed, but if you reopen it you will have to go to the emergency room. Take this." John handed him 2 large pills. "It's for the pain. You'll need to rest for a while. And make sure you apologize to Rosie. I'll go put her to bed."

"I will. Thank you, John," Sherlock gazed into his eyes, pure sincerity on his face.

"You're welcome, Sherlock."

John walked away and scooped Rosie into his arms.


	4. Chapter 4

"Dads!" Rosie called as she dashed up the stairs and burst through the door.

Sherlock looked up from his microscope raising and eyebrow as John mirrored his movement from behind the local paper.

"Yes, love?" John smirked as he watched his daughter practically bounce in place.

"I did it! I did it! I did it!" Rosie exclaimed.

"Did what?"

"I finished my study! I've been doing my very own study and I finished all my calculations in free period. Papa! Come here!"

"Yes, yes, I'm coming," Sherlock affirmed, waving his hand dismissively as he carefully moved the slide out from under the stage clips.

He then saundered over, plopped onto the chair across from John, and crossed his legs.

"So what's your experiment on?" John asked.

"It's not an experiment it's an _observational study_ ," Rosie corrected. "And it's about you!"

"Me?" John probed apprehensively.

"Yes, Daddy, you and Papa."

"You hear that Sherlock? Me _and_ you."

"Yes, John. So tell me, Watson, what were the findings of this _observational study_ of yours?"

"Well, there were several behaviors I observed that occurred when you two interact with each other and compared them to when you interact with your other friends like Mrs. Hudson and Mr. Lestrade."

"Rosie, why would you-"

"Shhh I'm not done yet. I counted the number of times you touched each other per hour and the length of these touches. I also timed the ratio of time you held eye contact to overall time, and counted how close to each other you stand compared to other people. I have concluded that Papa, you touch Daddy 1.2 times more than you do other people, and these touches last 3x as long. You also keep eye contact 4 times longer and stand 35 centimeters closer to Daddy compared to your friends on average. Daddy, you touch Papa 4 times as often as you do to your other friends and linger for 6 times longer. You hold eye contact 2 times longer and stand 26 centimeters closer on average compared to where you stand when talking to others. I also noticed that you both look at each other when the other isn't looking _a lot_ with this weird look on your faces, and Daddy looks at Papa's-"

"Rosie! Rosie, dear, that's enough."

Rosie was so invested in presenting her findings that she didn't even notice her dads' reactions.

Sherlock was staring intensely at John, eyes wide, now perching on the couch cushion like a cat about to leap, and John was cupping his hand over his face, blush slowly creeping up his neck.

"No! I haven't even told you the hypothesis yet! So anyways, I didn't get data on those last few things _but_ I made some charts and graphs of the other behaviors in free period." She pulled them out of her bag and forced a few papers onto her parent's laps "See? Evidence! Oh yeah! I almost forgot! So my hypothesis was that you two-," she jabbed a finger at them for emphasis, "are idiots! You _like_ like each other! I knew it all along but I needed proof, so I did research on how people who like each other act when they're with each other and then I watched."

At this point, the jaws of both accused men were gaping comically as they stared at their daughter.

"She's been spending way too much time with you, huh?" John put in, breaking the silence, but Sherlock seemingly didn't notice. He was staring straight ahead, perhaps processing this information, forming his own analysis.

"Well, anyways, I'm gonna go do my homework and then eat and then I'm going to Kristie's house," Rosie stated, walking away.

"Rosie, I don't remember you asking me if you can go to Kristie's house today," John stated.

"Yeah, 'cause I didn't. But don't worry, her mum said it's fine.

"Yeah, but _I_ didn't-" John attempted, but Rosie strolled off to go downstairs to her room in 221C.

"Okay. Right. Okay. Great," John prattled.

At the sound of the door, Sherlock snapped back into reality.

"John."

John swallowed. "Yeah?"

Sherlock turned his head to look at him. John couldn't help but to compare him to an owl, his eyes frantic as he precariously balanced on his toes pressing down into the cushion.

"She's right. We're idiots."

"Yes, s'pose we are."

Sherlock's gaze focused into a laser point as he propelled himself off his spot and almost into the chair John was hunched in, landing on his feet directly in front of it.

"You aren't denying it."

"No. No, I'm not. It's all here in charts, isn't it?" He tossed the crudely drawn papers off his lap onto the floor next to him.

"Yes. Brilliant."

"Hmm?"

"She's brilliant, using science so we couldn't just deny and pretend. Watson knows just how to get under our skin."

"Yeah well she does have a genius for a father."

"Two. Two geniuses. And her mother wasn't a complete moron either."

John scoffed. "Yeah, guess you're right." His eyes beamed as he met Sherlock's gaze. "Never thought I'd hear you call me a genius."

"Don't be absurd, John. You did go to medical school after all. Plus, after so many years with me you've caught on to some of my methods."

"So it's true, then. Her hypothesis, I mean," John cautioned.

"Yes, I do believe there is plenty of evidence to support it. I came up with 57 more examples in the past 5 minutes."

"Good. Great," John smirked. "So I guess this means… I suppose now we…"

John stood up from his chair, almost chest to chest with Sherlock, who was crowding so close. He reached his hand around the back of Sherlock's neck and gently pulled him downwards until their lips met and moved softly against one another.

John released him, the two of them glowing.

"Ahem, so, you ' _like_ like' me then?"

"Please, John. We are _not_ calling it that," Sherlock pouted.

John quickly placed a peck on that pout, making it go away instantly.

"So what shall we call this then?" he teased.

"Love. I love you."


End file.
